In earthing equipment for a switchgear using bare conductors for a main circuit, because the conductors in the main circuit are bare conductors, there is an advantage that an earthing work during a maintenance and inspection work can be performed from any arbitrary portion of the conductors, however, the energized portion thereof is exposed in a bare state, there is a danger of electrical shock depending on circumstances.
Namely, under a completely no voltage condition in an electric power installation, namely, in an instance of complete shutdown, there is no danger of electrical shock, however, when a maintenance and inspection work is performed while shutting down the load side under an active condition of bus bars in a main circuit (under a partial shutdown), the work has to be performed at portions near an active line, which is very dangerous.
On the other hand, in a switchgear using insulated bus bars covered by an insulator such as epoxy, such danger of electrical shock can be avoided even when the bus bars are in an active condition, and an earthing work can be performed at a portion where built-in apparatus are disposed that are main circuit contacts inside a panel.
However, even in such switchgear using insulated bus bars, it is dangerous to perform an earthing work while a worker getting into inside the panel, and the work efficiency is not desirable. For this reason, a drawer type carrying cart for earthing is proposed which permits to earth main circuit bus bars by placing an equipment main body on a stage of a distribution panel (switchgear) and by pushing in the same in a like sequence when attaching and detaching such as a circuit breaker (for example, see patent document 1: JP-A-11-69518).
In the drawer type carrying cart for earthing as referred to above, from a view point of enhancing adaptability to specification modification of the distribution panel, a measure is employed in which a mechanism of moving the carrying cart for earthing is used in common with that for circuit breakers in respective stages.
However, due to differences of earthing portions (stages of switchgear) where the main circuit of the switchgear is earthed, there sometimes happens that a position of a connecting portion to a bus bar of the main circuit does not match to a position of an earthing terminal of the carrying cart for earthing. In such instance, a plurality of carrying carts for earthing have to be manufactured in which a contact for earthing that matches to a connecting portion to a bus bar of the main circuit and a manipulating mechanism for earthing are respectively different, therefore, the cost of building such installation becomes expensive.
Further, because the structures of the respective carrying carts are different, when apparatus on the carrying carts for earthing malfunctions, since the common use and arrangement of the constitutional parts are disturbed, a new production of parts is also necessitated, and in addition a problem also arises that a significant amount of time and expense for the exchanging work is incurred.